Polymer composition from mixed plastic waste

Abstract

A process for making polymer composition from mixed plastic waste is disclosed. The composition comprises plastic waste of different types obtained from recycled unidentified, uncleaned, unsorted, compacted and homogenized plastic waste. Preferably the plastic waste comprises polyethylene (PE), approximately 50-60% of its total volume; polypropylene (PP), approximately 20-30% of its total volume; polystyrene (PS), approximately 5-10% of its total volume; a mixture of unidentified plastic and other materials, approximately 1-10% of its total volume. The mixture of unidentified plastics comprises polyamides (PA), Polyethylene terephthalate (PET), Polyacetal (POM), and Polycarbonate (PC).

Claims

1. A process for obtaining a polymer composition from mixed small volume weight of between 0.1-0.4 ton/m.sup.3 and large volume weight of more than 0.4 ton/m.sup.3 plastic waste, comprising: (a) separating mixed plastic waste from other waste flows; (b) baling the mixed plastic waste; (c) separating the small volume weight and the large volume weight plastic waste; (d) preparing a first raw material from the small volume weight plastic waste by the steps consisting of: breaking up the small volume weight plastic waste, separating non-plastic waste from the small volume weight plastic waste, melting of the small volume weight plastic waste, compacting the small volume weight plastic waste, breaking up the compacted mass into pieces sized at 3-10 mm to obtain an agglomerate fraction, and homogenizing the agglomerate to obtain the first raw material comprising 50-60% of polyethylene (PE) based on its total volume; 20-30% of polypropylene (PP) based on its total volume; 5-10% of polystyrene (PS) based on its total volume; and 1-10% of unidentified plastic and other materials based on its total volume; (e) preparing a second raw material from the large volume weight plastic waste by the steps consisting of: breaking up the large volume weight plastic waste-into pieces sized between 3 mm and 10 mm, separating non-plastic waste from the large volume weight plastic waste, drying the large volume weight plastic waste, and homogenizing the large volume weight plastic waste to obtain the second raw material comprising PS, LDPE, HDPE, HIPS, ABS, PC, PS/PP compounds; PP/HD compounds and unknown type of plastics; (f) mixing the first raw material and the second raw material; (g) adding a mixture comprising of polystyrene (PS), polypropylene (PP) and additive selected from the group comprising of pigments in PE-carrier, UV protective agents, antioxidants, foaming agent, mineral and structure supplementing additives, glass fiber substances, textile fiber substances, mineral additives and any combination thereof; and h) obtaining the polymer composition having density of 979-1026 kg/m.sup.3; melt flow index (g/10 min.) of 2-5; melting temperature of 165-180 C.; tensile modulus (elongation 50 mm/min.) of 794.97-864.70 Mpa; tensile stress at maximum load (elongation 50 mm/min) of 18.11-21.04 MPa; impact strength Charpy (Hammer 4 J) of 1348-1938 kJ/m.sup.2, and heat deflection temperature of 79-81 C.

2. The process of claim 1, wherein during the drying process of the large volume weight plastic waste in step e) a moisture content of the large volume weight plastic waste is decreased below 1%.

3. The process of claim 1, wherein during the compacting process of volume of the small volume weight plastic waste in step d) the volume of the small volume weight plastic weight is compacted approximately ten times.

4. The process of claim 1, wherein during the compacting process of the small volume weight plastic waste in step d) a moisture content of the material is reduced below 1%.

5. The process of claim 1, wherein the agglomerate fraction obtained in step d) has density of 380-450 kg/m.sup.3.

6. The process of claim 1, wherein the compacted small volume weight plastic waste obtained in step d) has density of 950-1050 kg/m.sup.3.

7. The process of claim 1, wherein the homogenization in step d) is performed with temperatures 115 C. to 165 C.

8. The process of claim 1, wherein the obtained polymer composition comprises: recycled small volume weight plastic waste, approximately 50-75% of total volume; recycled large volume weight plastic waste, 10-25% of total volume; polystyrene (PS), 5-20% of total volume; polypropylene (PP), 5-20% of total volume; and the additives, 0.2-10% of total volume.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained more precisely with references to figures added, where:

(2) FIG. 1 presents unidentified, uncleaned, unsorted mixed plastic waste of small volume weight;

(3) FIG. 2 presents the compacted and homogenized fraction of the polymer composition of the present invention according to the preferred embodiment, recycled from mixed plastic waste presented in FIG. 1;

(4) FIG. 3 presents unidentified, uncleaned, unsorted mixed plastic waste of large volume weight;

(5) FIG. 4 presents the compacted and homogenized fraction of the polymer composition of the present invention according to an alternative embodiment, recycled from mixed plastic waste presented in FIG. 3;

(6) FIG. 5 presents the fraction of the polymer mixture composition of the present invention according to another alternative embodiment, recycled from mixed plastic waste presented in FIG. 2 and FIG. 4;

(7) FIG. 6 presents a sample product profile obtained from the polymer composition of the present invention presented in FIG. 5;

(8) FIG. 7 presents the congealed molten mass (mixture A1) of the polymer composition of the present invention presented in FIG. 2;

(9) FIG. 8 presents the congealed molten mass (mixture A2) of the polymer composition of the present invention presented in FIG. 2;

(10) FIG. 9 presents the congealed molten mass of the single-type identified polypropylene plastic, known from the state of the art;

(11) FIG. 10 presents the congealed molten mass of the polymer composition of the present invention presented in FIG. 5;

(12) FIG. 11 presents the block diagram of the process for obtaining the polymer composition of the present invention from the mixed plastic waste.

DETAILED DESCRIPTION OF THE INVENTION

(13) The polymer composition of the present invention from mixed plastic waste comprises a homogeneous polymer mixture recycled from unsorted, unidentified, uncleaned plastic waste of different densities, various colours, small volume weight and/or large volume weight.

(14) The polymer composition of the present invention presented in FIG. 2, from compacted and homogenized mixed plastic waste comprises plastic waste of different types, and according to the preferred embodiment the polymer composition is obtained from recycled unidentified, uncleaned, unsorted plastic waste of small volume weight, containing: polyethylene (PE), approximately 50-60% of its total volume; polypropylene (PP), approximately 20-30% of its total volume; polystyrene (PS), approximately 5-10% of its total volume; a mixture of unidentified plastic and other materials, approximately 1-10% of its total volume.

(15) The properties of the polymer composition are as follows. Density of the material in agglomerated phase: 380-450 kg/m.sup.3

(16) Density of the material in melted and solidified phase: 950-1050 kg/m.sup.3 Melt flow index (g/10 min.): 1-5, preferably 2.5-3.5 Melting temperature: 165-180 C. Color: grey Moisture content: below 1% Fraction size: up to 10 mm Tensile modulus (Elongation 50 mm/min): 642.76-854.28 MPa Tensile stress at maximum load (Elongation 50 mm/min): 14.6-17.01 MPa Flexural modulus (Bending rate 20 mm/min): 1126-1723 MPa Impact strength Charpy (Hammer 4 J): 1,938-3,544 kJ/m.sup.2 Heat deflection temperature: 80-82 C.

(17) The unidentified plastic material portion of the polymer composition comprises, e.g. polyamides (PA), Polyethylene terephthalate (PET), Polyacetal (POM), Polycarbonate (PC). According to an alternative embodiment of the polymer composition of the present invention from mixed plastic waste, the composition comprises unidentified, uncleaned, unsorted, homogenized plastic waste of large volume weight: polyethylene (PE), approximately 50-60% of its total volume; polypropylene (PP), approximately 20-30% of its total volume; PS, ABS, PC, HIPS, approximately 5-10% of its total volume; mixture of unidentified plastic and other materials (e.g. sand, soil, organics, etc.), approximately 1-10% of its total volume.

(18) According to the alternative embodiment of the polymer composition of the present invention from mixed plastic waste, the composition additionally comprises recycled unidentified, uncleaned, unsorted, plastic household waste of large volume weight, whereas the recycled plastic waste of large volume weight comprises polypropylene (PP), HD polyethylene (HDPE), LD polyethylene (LDPE), polystyrene (PS), ABS, PET, PS/PP compounds, PP/HD compounds, other unidentified types of plastic material. The approximate plastic waste content of this polymer composition is as follows: recycled plastic waste of small volume weight, approximately 50-75% of the total volume, and plastic waste of large volume weight, approximately 25-50% of the total volume.

(19) The examples of such embodiment are presented in FIGS. 7 and 8, whereas larger PET content is evident in FIG. 7 in the form of unmelted pieces.

(20) According to an alternative embodiment of the polymer composition of the present invention, the composition comprises a mixture of recycled unidentified, uncleaned, unsorted plastic household waste of small and large volume weights, with a component X and additives Y added to it, whereas the component X is preferably either a single-type polymer or a mixture of single-type polymers made up from polystyrene (PS) and polypropylene (PP), chosen from a sorted source, and having been added in such a ratio that the polymer composition obtained comprises: recycled plastic waste of small volume weight, approximately 50-75%, and preferably 55-60% of the total volume; recycled plastic waste of large volume weight, approximately 10-50%, and preferably 10-25% of the total volume, and additionally; polystyrene (PS), approximately 5-20% (preferably 5-15%) of the total volume, and polypropylene (PP) approximately 5-20% (preferably 5-15%) of the total volume, and additives Y approximately 0.2-10%, preferably 1-5%.

(21) The properties of the polymer composition are as follows. Density of the material: 979-1026 kg/m.sup.3 Melt flow index (g/10 min.) approximately 2-5 Melting temperature: 165-180 C. Tensile modulus (Elongation 50 mm/min): 794.97-864.70 Tensile stress at maximum load (Elongation 50 mm/min): 18.11-21.04 MPa Flexural modulus (Bending rate 20 mm/min): Impact strength Charpy (Hammer 4 J): 1,348-1,938 kJ/m.sup.2 Heat deflection temperature: 79-81 C.

(22) As the additives Y, e.g. pigments in PE-carrier, UV protective agents, antioxidants, foaming agent, mineral and structure supplementing additives, glass fibre substances, textile fibre substances and/or mineral additives have been added.

(23) To make plastic materials of different types mix with each other in the course of subsequent recycling of the composition of the present invention, the results of experiments have shown that the composition should comprise a sufficient quantity of polymers of similar properties and similar molecular formulas. According to the most preferable embodiment these are polystyrene and polypropylene, with the preferred content in the composition being 5-15%.

(24) The composition is obtained from plastic waste of small volume weight has 70-90% of PE/PP, having a similar molecular formula. The molten mass of the plastics with similar molecular formulas will dominate when melted. The polymer composition is obtained from plastic waste of large volume weight also has 70-90% of PE/PP, having a similar molecular formula. The molten mass of the plastics with similar molecular formulas will dominate when melted.

(25) Due to that, when the mixture obtained from plastic waste of large volume weight (presented in FIG. 4) is additionally added to the composition obtained from plastic waste of small volume weight (presented in FIG. 2), then by melting such a polymer composition of the alternative embodiment of the present invention (presented in FIG. 5), the molten mass of the plastics with similar molecular formulas will dominate.

(26) Components X and additives Y are additionally added as substances controlling the subsequent production process as appropriate, i.e. the behaviour of the molten plastic mass is controlled through them in the course of recycling the composition.

(27) Experiments have shown the property of the polypropylene (PP) to move within the surface layers of the mass molten in the course of the recycling process of the mixed plastic waste composition, binding the previous mass of polymers of similar molecular formulas, obtained on the basis of plastic waste of small and large volume weights. The product surface is formed when coming into contact with the wall of the product cooling mould, non-permeable to gases.

(28) Experiments have shown the property of polystyrene (PS) to move within the middle layers of the molten mass of the mixed plastic waste composition. As the cooling rate of polystyrene (PS) is higher than that of the rest of the mass of the mixed plastic waste composition, and polystyrene (PS) is located in the middle layers of the molten mass, cooling the product will create a product structure not allowing the product to collapse.

(29) Sufficient mixing of polystyrene (PS) and the rest of the molten plastic mass in the molten state of the polymer composition of the present invention and under pressure, ensuring the homogeneity and durability of the product, preserves porous content for the product, and this in turn yields ca. 0.5-0.8 t/m.sup.3 as the potential density of the product.

(30) When, e.g. a foaming agent is added by manufacturing products from the polymer composition of the present invention, formation of gases in the molten plastic mass is stimulated, at the time of its cooling the gases start to expand, and seek a way out from the molten plastic mass. The volume weight of the end product can be changed by varying the dosages of the foaming agent. At the time of cooling the gases start to expand, and seek a way out from the molten plastic mass. Polypropylene moves within the surface layers of the molten mass during the process, binding the former mass of similar molecular formula with itself, and momentarily forming a layer non-permeable to gases, when coming into contact with the cold calibrator wall. Polystyrene moves within the middle layers of the molten mass. As the congealing rate of polystyrene (PS) is higher than that of the rest of the mass, and it is located in the middle layers of the molten mass, a structure not allowing the product being manufactured no longer to collapse, is created at the time of cooling. Sufficient mixing of polystyrene (PS) and the rest of the molten plastic mass in the molten state and under pressure takes place at the same time, ensuring the homogeneity, and preserving porous content for the product, that in turn yields ca. 0.5-0.8 t/m.sup.3 as the density of the profile.

(31) To improve the quality, polystyrene (PS) and/or polypropylene (PP) is additionally added to the polymer composition, obtained from the unidentified, uncleaned, and unsorted plastic household waste mixture of small and large volume weights of the present invention. For example, according to the embodiment presented in FIG. 7, polystyrene (PS) and polypropylene (PP) are additionally added to the mixture, approximately 12% of both.

(32) A test specimen of very good quality, obtained with a test melting equipment can be seen in case of the embodiment presented in FIG. 8. The surface structure is uniform, with light gloss. This indicates the pureness and quality of mixture A. In case of such embodiment polystyrene (PS) and polypropylene (PP) are additionally added to the mixture, approximately 5% of both.

(33) FIG. 2 presents the polymer composition of the present invention. Granulated plastic waste, obtained by recycling a single-type polymer could have a similar appearance. The differences between the polymer composition of the present invention, and a granulated single-type polymer are clearly evident when comparing their hardened molten masses.

(34) Hardened molten masses of the preferred embodiment of the polymer composition of the present invention are presented in FIG. 7 and FIG. 8. Less uniform fusing due to the foreign matter (sand, organic matter, soil, dust, paper) present in the plastic mixture is clearly visible. Virtually no gloss is evident. The test specimen can be broken in half by hand.

(35) Hardened molten mass of similar appearance, known from the state of the art, obtained from a single-type polymer is presented in FIG. 9 for comparison. In this case the hardened molten mass has been obtained from sorted and washed single-type plastic material, more specifically polypropylene (PP). The quality of fusing is clearly visible, no lumpiness is evident, the mass of plastic has congealed uniformly. Very hard to break by hand.

(36) The test specimen corresponding to mixture C is presented in FIG. 10. The quality of mixture C is primarily assessed visually. The test specimen shown in FIG. 9 has been used as reference. The more uniform the fusing quality, the higher the quality of mixture C, that directly affects the efficiency of the production process, to achieve the product shown in FIG. 6.

(37) FIG. 11 presents the block diagram of the process for obtaining the polymer composition of the present invention from the mixed plastic waste. The polymer composition of the present invention, obtained from mixed plastic waste comprises a homogeneous polymer mixture recycled from unsorted, unidentified, uncleaned plastic waste of different densities, various colours, small volume weight and large volume weight.

(38) Collected plastic waste of small volume weight, separated from other waste flows, and pressed together, are conveyed to the plastic waste recycling line where preliminary breaking up is performed; after that non-plastic waste is separated (e.g. by way of magnetic and air separation), and the preliminarily broken-up mixture of plastic waste is routed to recycling. The plastic waste is also mixed during the separation. Plastic waste of small volume weight is compacted in the course of recycling as plastics of this type have large cubages and are light volatile. Additional disintegration is performed during the compacting process, accompanied by continuous mixing and heating of the plastic mixture, until melting of the plastic mixture. As the plastics are dirty, other organic or inorganic material, still remaining in the plastic waste after the preceding separation of the non-plastic waste, is also destroyed or melted into uniform mass in the course of the breaking up, mixing and heating process.

(39) The compacting process is completed by quick cooling of the obtained mixture, and subsequent breaking up of the hardened mass to a fraction having a size of approximately 1 to 10 mm, preferably 5.1 to 10 mm. The agglomerate obtained is then routed to homogenisation.

(40) The volume of the plastic mixture is compacted approximately ten times in the course of this process. The mass of plastic waste transformed to the molten state in the course of the compacting process is rapidly cooled. For example cooled water, preferably at the temperature of approximately 4 C. to 10 C., is added to it, resulting in the molten mass hardening within a short space of time.

(41) The blades of the compacting equipment, initially used to break up the plastic mixture and mix the molten mass, start to break up the hardened mass. Breaking up is performed until obtaining an agglomerate of uniform fraction.

(42) The compacting system reduces the cubage of plastic waste, increases their density, mixes the plastic waste in the molten state, destroys the organic and bacterial material, and creates a stable material mixture, with a fraction size of approximately 3 to 10 mm, and moisture content below 1%, suitable for the subsequent production process. For example, a device with its blade system equipped with the drive and power unit sufficient to operate the blade system during the mixing and breaking up various plastic materials, and after that during the breaking up of the mass of hardened plastics, has been used as the compacting system. The blades of the blade system have been designed so as to enable them to break up the plastic waste mixture, mix this mixture in its molten state, and also function as the disintegrating mechanism after cooling the melted mass until its hardening. Further, a heating mechanism is additionally added to the compacting system, if required. As a result of the high temperature created in the course of the compacting system process, the temperature of the agglomerate obtained is approximately 115 C. to 165 C. when conveyed out of the compacting system.

(43) The agglomerate obtained is routed to drying and homogenisation, in the course of which the material mixture is mixed through, and a material of uniform properties is obtained. Unlike the generally known processes that route the compacted clean single-type polymer materials to subsequent regranulate production, according to the present invention the material passes through an additional cooling cycle lasting several hours, during which the material is mixed, and gradually cooled, this way stabilising the properties of the polymers for the subsequent production cycle.

(44) The after-cooler is designed to preserve the plastic properties and fraction of the material. After the after-cooling, the material is conveyed to the homogenisation system where mixing of the material takes place. The homogenisation system comprises a container mixer of at least 28 m.sup.3, enabling to mix the materials with each other, and homogenise the raw material mixture by batches of at least 10 to 15 tons. Unlike known container mixers, inflow of warm air has been added to the container mixer of the present solution, to also achieve efficient drying along with the mixing.

(45) Collected plastic waste of large volume weight, separated from other waste flows, and pressed together, is broken up, non-plastic waste is separated from it, it is dried, if necessary, and homogenized. Plastic waste of higher density (from 0.4 tons per m.sup.3) is broken up to a fraction of 3 to 10 mm in the course of the production process. The polymer materials are mixed in large quantities starting from 5 tons in the drying mixer tower and homogenisation tower. The homogenisation process unifies the properties of the polymers, and the drying process decreases the moisture content of the materials below 1%. Unlike known container mixers, inflow of warm air has been added to the drying mixer tower to obtain the polymer mixture of the present invention, so efficient drying would also be achieved along with the mixing.

(46) After compacting and homogenisation of the mixed plastic waste of small volume weight, and homogenisation of the plastic waste of large volume weight, mixing of the plastic waste of small volume weight and the plastic waste of large volume weight is performed to obtain the polymer composition of the invention, whereas the percentage of the material mixture produced from the plastic waste of small volume weight is approximately from 50% to 75%, and the percentage of the material mixture produced from the plastic waste of large volume weight is approximately from 25% to 50%.